对钢铁加热时，其颜色会随着温度上升而发生变化。
参考答案：对
图中表示四处热力环流形成示意过程，其中不正确的是
B．B
C．C
D．D
Hurry up! The train ______. You know it______ at 8:30 am.[ ]
A. leaves; leaves
B. is leaving; is leaving
C. leaves; is leaving
D. is leaving; leaves
